Coolable annular support for intentionally cooled piston rings and method for the production thereof

ABSTRACT

The invention relates to a coolable annular support ( 1 ) for internally cooled piston rings, comprising an annular body ( 2 ) embodied as a circular ring and a cooling channel plate ( 3 ), the cooling channel plate ( 3 ) being a component of the cooling channel, and a method for the production thereof. The components forming the annular body ( 2 ) and the cooling channel plate ( 3 ) are connected together by means of laser beams from at least one laser in a continuous wave operation. The cooling channel plate ( 3 ) is U-shaped and has openings ( 6 ) which act as an inlet or an outlet for the cooling material in conjunction with tubular-shaped bodies. It is possible to simultaneously compensate variations in volume by different air temperatures during welding. At least one edge of the annular body ( 2 ) and the cooling channel plate form a cavity ( 5 ) for the cooling material by connecting the end areas of the limbs of the cooling channel plate to said edge of the annular body ( 2 ). The connections of the annular body ( 2 ) and the cooling channel plate ( 3 ) takes place by means of one or more overlapping weld seams ( 4 ), so that a sealing connection between said two components is guaranteed.

BACKGROUND OF THE INVENTION

The invention relates to coolable annular supports for internally cooledpiston rings, comprising an annular body embodied as a circular ring,and a cooling channel plate, whereby the cooling channel plate is a partof the cooling channel, and to methods for the production thereof.

DE 40 40 611 C2 (jet piston cooling) and DE 44 38 703 A1 (light metal oraluminum piston with cooling channel for internal combustion engines)describe a piston cooling according to which a hollow space as a coolingchamber is disposed in the body of the piston. An additional element isnot required, although therewith a not simple and economical realizationof a hollow space in the body of the piston results.

DE 41 31 275 C2 (built-up liquid-cooled piston) describes a coolablepiston that is comprised and assembled of a plurality of parts. Theparts have recesses that form cooling channels and are interconnectedvia connection elements, such as screw connections. The production ofthe pistons requires assembly, and due to the use of positiveconnections, higher expenses are required for the sealing of the coolingchannels. In DE 42 08 037 A1 (multi-part, cooled piston for internalcombustion engines) the cooling channel is formed by a groove in thepiston body that is closed off by a two-part cup spring. The sealingtightness is supposed to be ensured by the cup spring, which againrequires increased structural expenses.

In DE 197 01 085 A1 (method and arrangement for the production of anannular support piston), a cooling channel is formed behind an annularsupport. For this purpose, a core for the formation of the coolingchannel is introduced into the mold, and the channel is closed offtoward the outside by the introduction of the annular support. Again,increased expenses are necessary for sealing the cooling channel.

Finally, in DE 199 33 036 A1 (cooling channel piston for an internalcombustion engine), a cooling channel is formed from an annular supportcomponent having two grooves, and the piston itself. The annular supportcomponent must again be connected with the piston in a tight or sealedmanner so that no coolant can pass into the combustion chamber.

The invention is based on the problem of economically and convenientlyproducing, with high quality, sealed, coolable annular supports forinternally cooled piston rings.

SUMMARY OF THE INVENTION

The coolable annular supports for internally cooled piston rings, whichsupports comprise an annular body embodied as a circular ring, and acooling channel plate, whereby the cooling channel plate is a part ofthe cooling channel, and the method for producing the same, arecharacterized in particular by a straightforward operability. Thecomponents in the form of the annular body and of the cooling channelplate are interconnected via laser beams of at least one laser in the cwoperation. The cooling channel plate has a U-shaped configuration and isprovided with a plurality of openings, advantageously in at least oneleg. In conjunction with tubular bodies, these openings serve for theentry or discharge of the coolant. A further advantage resulting fromthe openings is that fluctuations in volume caused by differenttemperatures of the air during the welding do not, to the greatestextent possible, lead to cracks or gaps of the weld seam, annular bodyand/or cooling channel plate that is to be cooled. The different airpressures can be equalized with the atmosphere by the openings.

At least one edge of the annular body, and the cooling channel plate,form a hollow space for the coolant by the connection of the end regionsof the legs of the cooling channel plate with this edge of the annularbody. In this way, a very straightforward and economical realization ofthe coolable annular support for internally cooled piston rings results.

The connections of the annular body and of the cooling channel plate areeffected via a plurality of weld seams, thus ensuring a tight and sealedconnection between these two components. For this purpose, the laserbeams are guided with an offset in the direction of the respectivelygreatest quantity of material, so that different thermal conductivitiesof the components are compensated for during the formation of therespective weld seam. Furthermore, the path and movement of the coolableannular support or of the laser beams is greater that 360° relative tothe coolable annular support. In so doing, the not yet completely formedweld seam is equalized during the heating-up phase after turning on thelaser after positioning thereof, accompanied by simultaneous movement ofthe coolable annular support or of the laser beams relative to thecoolable annular support. A high power that is otherwise necessary atthe start is avoided, so that at the same time a danger, caused thereby,of a burning through, with holes resulting therefrom, is avoided to amaximum extent.

A further advantage results from the mounting of the tubular bodies.These represent conduits for the coolant. Otherwise, the cooling channelis bored after the casting of the piston. The boring is a cuttingprocess, whereby chips or shavings can also pass into the coolingchannel. As a result, the cooling channels of pistons manufactured inthis manner must be rinsed. This is no longer necessary with theinventive annular supports, thus providing very favorable and economicalconditions. A further advantage is that the tubular bodies can at thesame time serve as supports for the annular support in the mold for thecasting of the piston. This results in a manageable and fixed functionalunit that can be placed into the casting mold of the piston. The tubularbodies end externally of the piston, so that the cooling channelsprovided thereby are freely accessible. For this purpose, the tubularbodies face in the direction of the crankshaft, so that inlets andoutlets of the cooling fluid for the coolable annular support are easilyaccessible. This results in a very advantageous manufacture of pistonshaving coolable annular supports. A further advantage of the tubularbodies is that even during the casting of the piston with the coolableannular supports, fluctuations in volume can be compensated for. Cracksor pores caused thereby are avoided to a maximum extent.

A further advantage of the coolable annular supports is that prior tothe casting of the piston they can be checked for a tight seal, so thatonly sealed coolable annular supports can be used during the manufactureof the piston. The result is sealed pistons.

Plate-shaped bodies that close off the openings result in a closed-offhollow space as a cooling channel. Known, coolable annular supports arethereby provided with which bores introduced into the piston and thecooling channel form the cooling channels. Tubular bodies as coolingchannels can, of course, also be introduced into these bores.

A plurality of coolable annular supports, which are disposedsymmetrically and parallel to one another, and which are provided with aplurality of tubular bodies that are disposed between them and that faceoutwardly, represent a compact construction. This can easily be placedin the mold of the piston, thus resulting in a straightforward and veryeconomical realization of the piston having coolable annular supports. Afurther advantage comprises the possibility of checking the sealingtightness of the assembly. The quality of such pistons increasesconsiderably.

An arrangement of the end regions of the tubular bodies in the coolingchannel leads to a nozzle effect. The coolant enters in a directedmanner and swirls in the cooling channel, thus increasing the coolingeffect. This region of the tubular body can also decreasediscontinuously or continuously in cross-section in the direction of theend thereof, so that assuming a uniform pressure, a considerably greaterflow velocity of the coolant is achieved. The swirling or turbulence ofthe coolant in the cooling channel is increased considerably.

Favorable realizations of the connections between the legs of thecooling channel plate and the annular body are provided by a pluralityof weld seams. The outer weld seam or seams are overlaps, so that tightconnections can be produced. Cracks or gaps caused by the escape ofgases from the material of the cooling channel plate and of the annularbody are covered.

Advantageously, in addition to the first weld seam that connects thecomponents, in the direction of the annular body two further overlappingweld seams and in the direction of the cooling channel plate, a weldseam that overlaps the first lap seam are applied. These serve to covercracks and gaps that form in the annular body and in the cooling channelplate, so that a tight and sealed cooling channel is realized. Thesecracks and gaps result from the escape of gases from the annular bodies.

Placing the starting regions and the end regions of the weld seams atvarious locations of the respective arcs of the individual weld seamsensures tight and sealed connections of the cooling channel plate and ofthe annular bodies.

Favorable quantities of the metal powder supplied per weld seam are asfollows:

quantity for the second weld seam is less than the quantity for thefirst weld seam,

quantity for the third weld seam is less than the quantity for thesecond weld seam, and

quantity for fourth weld seam is the same or nearly the same as thequantity for the second weld seam.

The low quantities of the weld seams two to four serve to cover cracksand/or gaps that result from the escape of gases. Lower quantitieshaving equivalently lower capacities lead to a smaller melting or fusingof the respective material, thus reducing an escape of gases fromcomponents of these materials.

Favorable parameters are powers of greater than/equal to 900 W and lessthan/equal to 1800 W at advancement speeds of equal to/greater than 20mm/s and less than/equal to 100 mm/s. As a result, the regions of theannular body and of the cooling channel plate that are to be welded aremelted or fused in such a way that a tight and sealed connectionresults.

Embodiments of the invention are illustrated in the drawings and aredescribed in greater detail in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a diagrammatic illustration of a coolable annular support forinternally cooled piston rings, with openings for tubular bodies,

FIG. 2 a diagrammatic cross-sectional illustration of a coolable annularsupport for internally cooled piston rings, with an opening and atubular body,

FIG. 3 a diagrammatic sectional illustration of a plurality of coolableannular supports that are interconnected via a tubular body, and

FIG. 4 a cross-sectional illustration of a connection location betweenan end region of a leg of the cooling channel plate and the annularbody.

DESCRIPTION OF PREFERRED EMBODIMENTS

Subsequently, coolable annular supports 1 for internally cooled pistonrings, and methods for the manufacture thereof, are respectivelyexplained in greater detail together.

1. Embodiment

A coolable annular support 1 (illustration in FIG. 1) for internallycooled piston rings essentially comprises an annular body 2 and acooling channel plate 3. The cooling channel plate 3 is embodied in theshape of a circular ring, and in cross-section predominantly has a Ushape. The cooling channel plate 3 has openings 6, whereby these areadvantageously disposed in a leg. The cooling channel plate 3 isdisposed in the inner space of the annular body 2. The end regions ofthe legs of the cooling channel plate 3 are connected with at least oneedge of the annular body 2 in such a way that the inner surface of thecooling channel plate 3, and the edge of the annular body 2, delimit anannular hollow space 5. This hollow space 5 is the cooling channel for acoolant that flows through this cooling channel. For this purpose,tubular bodies 7 are connected with the cooling channel plate 3. FIG. 2diagrammatically illustrates a cross-section of a coolable annularsupport 1, including a tubular body 7. The cooling channel plate 3 andthe annular body 2 are interconnected in a tight and sealed manner viaweld seams 4. Employed is a Nd:YAG or high power diode laser in cwoperation (cw-continuous wave, constant radiation over time) with apower of greater than/equal to 900 W and less than/equal to 1800 W. Theconnection of a leg of the cooling channel plate 3 to the annular body 2comprises at least one weld seam 4. In this connection, during thewelding a metal powder is supplied as an additive in an inert gasatmosphere.

The weld seam, during the supply of laser beams, predominantly orentirely results on the annular body 2 by a partial melting or fusing ofthe annular body 2, a partial melting or fusing of the cooling channelplate 3, and a melting or fusing of the applied metal powder.

After the positioning of the starting region of the connection locationbetween the annular body 2 and the cooling channel plate 3, the laser isturned on. In so doing, accompanied by simultaneous starting of themovement of the annular body 2, including the cooling channel plate 3,relative to the laser beams, or in one embodiment of the movement of thelaser beams relative to the annular body 2, including the coolingchannel plate 3, there results, due to the starting delay of the laserbeams connected therewith, weld seams 4 that are not completely formedin this region.

The path of movement of the coolable annular support 1 or of the laserbeams is therefore respectively greater that 360°, whereby the start andfinishes of the weld seams 4 are disposed at various locations. Thespeed of advancement of the annular body 2, including a cooling channelplate 3, is equal to/greater than 20 mm/s and less than/equal to 100mm/s. A respective tubular body 7 is disposed on or in the opening 6,and by means of at least one further fifth weld seam 8, which isproduced with laser beams of the laser, is connected with the leg of thecooling channel plate 3 in such a way that the cooling channel and theinner space of the tubular body 7 form a common hollow space. In thisconnection, the end portion of the tubular body 7 advantageouslyprojects into the cooling channel. In so doing, the hollow space 5, asthe cooling channel of a coolable annular support 1, is accessible viatubular bodies 7. The tubular bodies 7 serve for the guidance of thecoolant.

2. Embodiment

A coolable annular support 1 (illustration in FIG. 1) for internallycooled piston rings essentially comprises an annular body 2 and acooling channel plate 3. The annular body 2 is, for example, a casting,e.g. an austenitic casting as A-graphite or E-graphite. The coolingchannel plate 3 is embodied in the shape of a circular ring, has incross-section a predominantly U shape, and comprises, for example, ahigh-quality or stainless steel. At least one leg of the cooling channelplate 3 has openings 6. The cooling channel plate 3 is disposed in theinner space of the annular body 2. The end regions of the legs of thecooling channel plate 3 are connected with at least one edge of theannular body 2 in such a way that the inner surface of the coolingchannel plate 3, and the edge of the annular body 2, delimit an annularhollow space 5. This hollow space 5 is a cooling channel for a coolantthat flows through this cooling channel. For this purpose, tubularbodies 7 are connected with the cooling channel plate 3. FIG. 2diagrammatically illustrates a cross-section of a coolable annularsupport 1, including a tubular body 7. The cooling channel plate 3 andthe annular body 2 are interconnected in a tight and sealed manner viaweld seams 4. Employed is a Nd:YAG or high power diode laser in cwoperation (cw-continuous wave, constant radiation over time) having apower of greater than/equal to 900 W and less than/equal to 1800 W. Theconnection of a leg of the cooling channel plate 3 with the annular body2 comprises four weld seams 4 a, 4 b, 4 c, 4 d. In this connection,during the welding for example a stainless steel powder is supplied asan additive in an inert gas atmosphere.

The first weld seam 4 a results by guiding laser beams predominantly orentirely onto the annular body 2 by partial melting or fusing of theannular body 2, partial melting or fusing of the cooling channel plate3, and melting or fusing of the applied stainless steel powder. Thesecond weld seam 4 b results from guidance of laser beams along theconnection between annular body 2 and first weld seam 4 a by partialmelting or fusing of the annular body 2, partial melting or fusing ofthe first weld seam 4 a, and melting or fusing of the applied stainlesssteel powder. The third weld seam 4 c results from guidance of laserbeams along the connection between cooling channel plate 3 and firstweld seam 4 a and predominantly or entirely on the first weld seam 4 aby partial melting or fusing of the cooling channel plate 3, partialmelting or fusing of the first weld seam 4 a, and melting or fusing ofthe stainless steel powder. The fourth weld seam 4 d is produced byguidance of laser beams along the connection between annular body 2 andsecond weld seam 4 b and predominantly or entirely on the second weldseam 4 b by partial melting or fusing of the annular body 2, partialmelting or fusing of the second weld seam 4 b, and melting or fusing ofthe stainless steel powder. FIG. 4 shows a sectional view of aconnection location between an end region of a leg of the coolingchannel plate 3 and the annular body 2. The quantities of stainlesssteel powder supplied per weld seam 4 are, in this connection,advantageously and by way of example as follows:

-   -   quantity of the first weld seam 4 a equals 100%,    -   quantity of the second weld seam 4 b equals 60% of the first        weld seam 4 a,    -   quantity of the third weld seam 4 c equals 30% of the first weld        seam 4 a, and    -   quantity of the fourth weld seam 4 d equals 60% of the first        weld seam 4 a.

The staggering of the laser beams are, in this connection, for example,greater than/equal to 0.1 mm and less than/equal to 0.2 mm. After thepositioning of the starting portion of the connection location betweenthe annular body 2 and the cooling channel plate 3, the laser is turnedon. In so doing, with simultaneous starting of the movement of theannular body 2, including the cooling channel plate 3, relative to thelaser beams, or in one embodiment of the movement of the laser beamsrelative to the annular body 2, including the cooling channel plate 3,due to the start-up delay of the laser beams connected therewith thereresult incompletely formed weld seams 4 in this region. The path ofmovement of the coolable annular support 1, or of the laser beams, istherefore respectively greater than 360°, whereby the starts and theends of the weld seams 4 are disposed at different locations. Theadvancement speed of the annular body 2, inclusive of the coolingchannel plate 3, is equal to/greater than 20 mm/s and less than/equal to100 mm/s. A respective tubular body 7 is disposed at or in the opening 6and is connected via at least one further fifth weld seam 8 produced bylaser beams of the laser with the leg of the cooling channel plate 3 insuch a way that the cooling channel and the inner space of the tubularbody 7 form a common hollow space. In this connection, the end region ofthe tubular body 7 advantageously projects into the cooling channel. Inso doing, the hollow space 5, as a cooling channel of a coolable annularsupport 1, is accessible via tubular bodies 7. The tubular bodies 7serve for the guidance of coolant.

In a further version of the specific embodiments, a plurality ofcoolable annular supports 1 can be disposed one above the other in sucha way that they have a common axis of symmetry (illustration in FIG. 3).The connection of the hollow spaces 5 of the coolable annular supports 1is effected via tubular bodies 7 between the coolable annular supports1. This results in a compact unit that can easily be placed in a moldfor the piston. The outer coolable annular support 1 that faces in thedirection of a crankshaft has outwardly facing and ending tubular bodies7 that serve for the guidance of the coolant to or from the coolableannular supports 1.

The specification incorporates by reference the disclosure of Germanpriority documents 101 33 724.8 and 201 11 527.1, both filed Jul. 6,2001, as well as PCT/DE02/02498 filed Jul. 4, 2002.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

1. A coolable annular support for internally cooled piston rings, comprising: an annular body (2) embodied as a circular ring; a cooling channel plate (3) in the form of a circular ring and having a predominantly U-shaped cross-section, wherein said cooling channel plate is provided with openings (6), wherein end portions of legs of said cooling channel plate (3) are respectively connected to edge portions of said annular body (2) by laser beams of at least one laser in a continuous wave operation, accompanied by a supply of metal powder and an inert gas, via overlapping weld seams (4) that are staggered in a direction of said annular body (2) and are each produced with a path of movement of greater than 360°, and wherein said end portions of said legs of said cooling channel plate (3) are connected to said edge portions of said annular body (2) in such a way that said cooling channel plate, and at least a surface of said annular body that delimits an inner space thereof, delimit a hollow space (5) as a cooling channel; and respective tubular bodies (7) or plate-shaped bodies disposed on or in said openings (6) and connected, via at least one further weld seam (8), with said legs of said cooling channel plate (3) in such a way that said cooling channel and an inner space of said tubular bodies (7) form a common hollow space or a closed hollow space is present.
 2. A coolable annular support according to claim 1, wherein a plurality of coolable annular supports (1) are disposed symmetrically and parallel to one another, wherein a plurality of tubular bodies (7) are disposed between said coolable annular supports (1), and wherein one of outer ones of said coolable annular supports (1) are provided with outwardly facing tubular bodies (7).
 3. A coolable annular support according to claim 1, wherein an end region of a respective tubular body (7) is disposed in said cooling channel in such a way that said end region projects into said cooling channel.
 4. A coolable annular support according to claim 1, wherein a connection location between a leg of said cooling channel plate (3), and said annular body (2), is a first weld seam (4 a), which is produced by a partial melting or fusing of said annular body (2), partial melting or fusing of the cooling channel plate (3), and a melting or fusing of applied metal powder, and a second weld seam (4 b), which is produced by a partial melting or fusing of said annular body (2), a partial melting or fusing of said first weld seam (4 a), and a melting or fusing of said applied metal powder, and wherein said second weld seam (4 b) is a weld seam that covers cracks and/or gaps in said annular body (2) occurring during a welding of said first weld seam (4 a).
 5. A coolable annular support according to claim 4, wherein said connection location is furthermore a third weld seam (4 c), which is produced by a partial melting or fusing of said cooling channel plate (3), a partial melting or fusing of said first weld seam (4 a), and a melting or fusing of said metal powder, and a fourth weld seam (4 d), which is produced by a partial melting or fusing of said annular body (2), a partial melting or fusing of said second weld seam (4 b), and a melting or fusing of said metal powder, and wherein said second, third, and fourth weld seams (4 b, 4 c, 4 d) are weld seams that cover cracks and/or gaps in said annular body (2) and said cooling channel plate (3) that occur during a welding of said first weld seam (4 a).
 6. A coolable annular support according to claim 1, wherein starting regions and end regions of said weld seams (4) are disposed at different locations of respective arcs of individual ones of said weld seams. 